SolarEdge ‘DC-DC optimiser’ technology in the UK

by Solar Selections on April 18, 2012

One of the trickiest parts of maximising efficiency in a solar PV installation is dealing with variations in power output among panels and strings of panels in the same system. SolarEdge is a leading company that has developed a unique solution to the problem of irregularity in solar panel array output. It uses a solar system architecture that utilises per-module maximum power point tracking (MPPT) to tackle system efficiency from a holistic design perspective, providing an ingenious balance of system strategy for solar system efficiency and energy savings.

Centralised MPPT inverters 

In order to explain the innovative inverter technology that SolarEdge specialises in, it is first essential to understand how conventional solar system inverters function.

System losses can sometimes be attributed to the nature of industry-standard crystalline solar panels themselves, which are susceptible to partial shading and overheating, and sometimes attributed to the nature of conventional inverters, which do not perform MPPT for individual modules.

There are many potential reasons for variation amongst panels in an array: natural variance in a solar panel’s rated capacity is typically +/-3% of rated output, shading can happen on some parts of the array but not others, the array can heat up unevenly, and strings of panels on different sides of the same roof can generate different amounts of electricity at different times of day.

In a system with a centralised-MPPT, single-input inverter, total solar system array output will be limited by the panel that is producing the least amount of power–the weakest link is where the chain breaks. If an inverter has only one input for one ‘string’ of panels, you may have to deal with losses on a regular basis, or buy more than one inverter to improve the overall system efficiency.

Some inverters support MPPT at a string level, which does help to minimise losses, but the inverter still cannot ‘see’ into a string to monitor and control what individual panels are doing. This means that your system is not taking full advantage of all the power produced by your panels, which in turn means higher cost per watt of your system and extended payback periods for your solar investment.

How Maximum Power Point Tracking (MPPT) works. (Image via SolarEdge) An example of partial shading in a conventional multi-string inverter system (Image credit: pvsolarchina.com)

SolarEdge Solar Power System Architecture: Holistic solar system design using module-level MPPT

The engineers at SolarEdge took a bird’s-eye-view approach to system design. An image on their homepage is telling of their methodical, thoughtful approach: transposed over a photograph of a Zen Buddhist rock garden read the words, “Good design always requires a holistic viewpoint. Take a step back, consider the details from above, and you get a better perspective on how to deal with the problems close up.”

Benefits of SolarEdge technology:

-Up to 25% increase in power output compared to single- and multi-input inverter system arrangements

-Superior inverter efficiency (up to 98%) – peak performance in both mismatched and unshaded conditions

-Flexibility in system design options: SolarEdge system architecture allows parallel uneven length strings, panels of different wattages and from different manufacturers (more inventory options); installation involves fewer components and less wiring, which means faster installation and better roof space utilisation than conventional systems

-Interactive, ‘from anywhere’ monitoring offers a new world of opportunities with regard to system troubleshooting maintenance

-The power optimizer (MPPT tracker) can be embedded into any module as a certified junction box–possible on-site or factory-based integration into solar modules

-Superior safety for installers and firefighters: Electric arc detection and termination features; safe module voltage when disconnected or off

-SolarEdge ‘Inverter Configuration Tool’ software means immediate installation feedback for quick system commissioning

How does SolarEdge distributed smart inverter technology work?

 

SolarEdge-Smart-Inverter-System-for-Efficiency SolarEdge System: Holistic system design for efficiency, cost-savings, and ease of monitoring. (Image from SolarEdge.com)

SolarEdge System Architecture Components:

Three components form the balance of system in SolarEdge’s ‘system architecture’.

-Module-embedded power optimisers, which monitor and regulate the power output of all the individual modules in an array, in order to maximise overall system output–these can be installed on-site, or may be pre-assembled in solar module factories of companies that are in a partnership with SolarEdge,

-A smart inverter, which inverts the DC power of all modules to grid compliant AC, and

-A monitoring system, data from which is accessible via the Internet.

SolarEdge System Architecture Features:

Module-level MPPT

The inverter uses a highly-optimised algorithm to keep each module at the same constant MPP, preventing power loss even under panel mismatch or partial shading. In fact, even panels from different manufacturers can be used simultaneously in the same array. (This offers intriguing possibilities for future applications in Building-Integrated Photovoltaics (BIPV); solar windows, solar walls, and rooftop solar arrays could all be routed through one inverter.) The algorithm also allows the system to react more effectively to changes in irradiance and temperature, a big benefit on cloudy days.

Highly Efficient DC Conversion

Each power optimiser performs a DC-DC power conversion (peak 99.5% efficiency) that allows it to boost or buck output voltage of modules in the array to ensure a fixed string voltage.

Fixed String Voltage

The voltage of a string is held constant at the optimal point for DC to AC conversion, regardless of the number of modules in a string, or external factors such as weather or shading. This feature means that there are fewer limits to system design and panel location, greater inverter efficiency and reliability, and lower installation costs.

Advanced Power-Line-Communication

A range of module-by-module status indicators (current, voltage, etc) are continuously measured and communicated by the power optimisers. Data are transferred through the existing DC power lines, meaning that there is no need for extra wiring. For ease in monitoring all the goings-on within the system, the inverter houses a LAN- and wireless-capable communications hub, enabling the owner or operator to view system performance in detail on a remote monitoring server from a computer or other even hand-held devices.

Performance data being recorded on a remote monitoring server also means that the system owner or operator can quickly identify and troubleshoot problems with your system, should any arise, minimising or eliminating the need for site visitations and associated travel charges.

SolarEdge: certifications, awards, and recognition

-ETL Mark: Proof of compliance with North American safety standards

-CE mark: Panel is compliant with European Union regulations

SolarEdge has also  been rewarded for its outside-the-box thinking with numerous awards, including the Climate Change Business Journal’s 2010 Business Achievement Solar Technology Merit Award, and the 2011 Red Herring Global 100 Award, where it was recognised for its achievements in the solar power optimisation field.

About SolarEdge

Founded in 2006, currently engaged in partnership agreements with module manufacturers and integrators in Europe, USA and Japan, which provide SolarEdge technology alongside their current services.

-Company Headquarters-

Hod Hasharon, Israel

Other offices in USA, Germany, and the Asia-Pacific region

© 2012 Solar Selections UK

Resources and Links:

SolarEdge Power Optimiser: Module-embedded solution (pdf)

 

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